Short-range wireless proximity networks typically involve devices that have a communications range of one hundred meters or less. To provide communications over long distances, these proximity networks often interface with other networks such as cellular networks, wireline telecommunications networks, and the Internet. IEEE 802.15.3 and IEEE 802.15.3a are examples of short-range wireless communications networks.
A high rate physical layer (PHY) standard is currently being selected for IEEE 802.15.3a. The existing IEEE 802.15.3 media access control layer (MAC) is supposed to be used as much as possible with the selected PHY. Currently, there are two remaining PHY candidates. One of these candidates is based on frequency hopping application of orthogonal frequency division multiplexing (OFDM). The other candidate is based on M-ary Binary offset Keying. The OFDM proposal is called Multiband OFDM (MBO). Moreover, in order to further develop the OFDM proposal outside of the IEEE, a new alliance has been formed called the MultiBand OFDM Alliance (MBOA).
MBO utilizes OFDM modulation and frequency hopping. MBO frequency hopping may involve the transmission of each of the OFDM symbols at various frequencies according to pre-defined codes, such as Time Frequency Codes (TFCs). Time Frequency Codes can be used to spread interleaved information bits across a larger frequency band.
Presently, there is an interest within the MBOA to create a Medium Access Control (MAC) layer that would be used with the OFDM physical layer instead of the IEEE 802.15.3 MAC layer. A current version of the MBOA MAC involves a group of wireless communications devices (referred to as a beaconing group) that are capable of communicating with each other. The timing of beaconing groups is based on a repeating pattern of “superframes” in which the devices may be allocated communications resources.
MAC layers govern the exchange among devices of transmissions called frames. A MAC frame may have various portions. Examples of such portions include frame headers and frame bodies. A frame body includes a payload containing data associated with higher protocol layers, such as user applications. Examples of such user applications include web browsers, e-mail applications, messaging applications, and the like.
In addition, MAC layers govern the allocation of resources. For instance, each device requires an allocated portion of the available communication bandwidth to transmit frames. The current MBOA MAC proposal provides for resource allocation to be performed through transmissions called beacons. Devices use beacons to convey non-payload information. Each device in a beaconing group is assigned a portion of bandwidth to transmit beacons.
This approach allows the MBOA MAC to operate according to a distributed control approach, in which multiple devices share MAC layer responsibilities. A channel access mechanism, referred to as the Distributed Reservation Protocol (DRP) is an example of such shared responsibility. DRP includes basic tools for establishing and terminating a unidirectional connection between two or more devices.
DRP allows devices to make a reservation for a certain period of the data portion of the superframe. The establishment of a reservation is referred to as DRP negotiation. To establish and maintain the reservation, a device requesting a reservation transmits a DRP information element (DRP IE) during its beacon slot. The peer device(s) for the reservation also transmit the DRP IE in their respective beacon slots. These devices continue to transmit the DRP IE in their respective beacon slots of each superframe during the existence of the reservation. A reservation can be made, for example, for a stream.
Devices may not receive a transmitted DRP IE for various reasons, such as the wireless transmission environment and device mobility. Unfortunately, the current MBOA MAC Specification (version 0.72, Oct. 20, 2004) does not offer a robust approach for handling such events. Instead, missing a beacon may result in devices having inconsistent perspectives on the status of a stream. Accordingly, a more effective approach is needed.